Erin Stellato shows us how to capture details when processes are blocked:
To view the output from extended events you can open the .xel file in Management Studio or query the data using the sys.fn_xe_file_target_read_file function. I typically prefer the UI, but there’s currently no great way to copy the blocking report text and view it in the format you’re used to. But if you use the function to read and parse the XML from the file, you can…
If you can’t buy a tool which monitors long-term blocking, you can still build it yourself pretty easily.